1. Field of the Invention
The present invention relates generally to bicycles. More particularly, the present invention relates to a bicycle frame preferably including a rear wheel suspension assembly suitable for use in connection with off-road bicycles.
2. Description of the Related Art
Off-road bicycles, or mountain bikes, may be equipped with front and rear suspension assemblies operably positioned between the front and rear wheels, respectively, and the frame of the bicycle. Providing front and rear suspension on a mountain bike potentially improves handling and performance by absorbing bumps, and other rough trail conditions, which may be encountered while riding off-road. However, because mountain bikes are typically pedal-driven, i.e., use the rider's power output to propel the bicycle, the provision of rear suspension, especially, may undesirably absorb a rider's power output, resulting in wasted effort.
Accordingly, rear suspension systems commonly incorporated on engine-driven vehicles, such as motorcycles, have proven ineffective for use with pedal-driven vehicles, such as mountain bikes. In addition, because a mountain bike is propelled solely by power output from the rider, it is desirable that the rear suspension assembly be lightweight. Rear suspension systems of engine-driven vehicles commonly emphasize strength over weight and, therefore, have not been widely incorporated on mountain bikes.
Mountain bike rear suspension designs utilizing multiple linkage members are currently used and are often effective at isolating pedal-induced and brake-induced forces from acting on the rear suspension. However, one problem associated with prior mountain bike rear suspension designs involves placement of the rear shock absorber. Due to the relatively complex nature of common mountain bike rear suspension assemblies, the placement of the rear shock absorber has often precluded the use of a traditional triangular mainframe of the mountain bike. For example, typical rear shock placement has either precluded the use of a vertical seat tube member of the mainframe, or has been positioned within the internal space defined by the mainframe. As the down tube and the seat tube members of the mainframe have traditionally been provided with mounts, or bosses, for mounting of water bottle cages, many designs incorporating rear suspension assemblies have inhibited the use of one, or both, of the traditional water bottle cage locations due to the placement of the rear shock absorber.
Another problem with prior art bicycles that incorporate front and rear suspension is that the frame designs that have evolved to provide increasing amounts of front and rear wheel suspension travel have not properly addressed the increased force that is imparted on the frame due to the increased moment arm resulting from the increased length of the front suspension fork.